Harvesters of this type typically have a telescoping container within which the stack is formed. One part of the container is comprised of an upper vertically reciprocating press, while the other part is comprised of a lower stationary section that telescopically receives the press. Completed stacks are discharged out the rear end of the container when the press is raised to its fullest extent at the completion of the forming process. While the rear end of the container must thus be open at the time of stack discharge, it is essential that it be closed during stack formation in order to prevent the material being compressed within the container from escaping during that action.
One way of achieving this objective has been to provide a door on the upper press which hangs in a suspended manner from an upper pivot point on the press. A cooperating gate on the lower section is hinged to the latter at the bottom of the gate and forms a ramp down which the stack may slide when the gate is fully opened. By having the gate overlap the suspended door adjacent the bottom of the latter, a single latch may be utilized in connection with the gate to maintain both the gate and the door closed during the forming process. Gravity may then be used to open the lower gate at the time of stack discharge, and the upper door may simply be allowed to swing upwardly and outwardly under the impulse of the discharging stack if so desired.
Where the stack itself is utilized to lift the upper door, the door can have a tendency to drag along the top of the stack and disturb the carefully prepared "crown" which is so contoured as to readily shed moisture instead of allowing it to penetrate deeply into the stack and spoil the hay. One way of alleviating this problem has been to employ one or more coil springs anchored to the door on the one hand, and the press itself on the other, so as to assist the stack in raising the door, the strength of the springs not being sufficient in and of themselves to power the door to its opened position.
Another alternative is illustrated in U.S. Pat. No. 3,901,142, in the name of Wood, which discloses a rather complex system of levers, bars, cranks, straps and other components so arranged that the upper door is cranked open as the press is raised from its lowermost position.